[all-commits] [llvm/llvm-project] 64af34: [libc] Implement expm1f function that is correctly...

[lntue via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 64af346b185ab3c3c34e145181717350c304b05a
      https://github.com/llvm/llvm-project/commit/64af346b185ab3c3c34e145181717350c304b05a
  Author: Tue Ly <lntue at google.com>
  Date:   2022-03-15 (Tue, 15 Mar 2022)

  Changed paths:
    M libc/src/math/generic/CMakeLists.txt
    M libc/src/math/generic/common_constants.cpp
    M libc/src/math/generic/common_constants.h
    M libc/src/math/generic/expf.cpp
    M libc/src/math/generic/expm1f.cpp
    M libc/test/src/math/exhaustive/CMakeLists.txt
    M libc/test/src/math/exhaustive/exhaustive_test.cpp
    M libc/test/src/math/exhaustive/exhaustive_test.h
    M libc/test/src/math/exhaustive/expm1f_test.cpp
    M libc/test/src/math/expm1f_test.cpp

  Log Message:
  -----------
  [libc] Implement expm1f function that is correctly rounded for all rounding modes.

Implement expm1f function that is correctly rounded for all rounding modes.  This is based on expf implementation.

>From exhaustive testings, using expf implementation, and subtract 1.0 before rounding the final result to single precision
gives correctly rounded results for all |x| > 2^-4 with 1 exception.  When |x| < 2^-25, we use x + x^2 (implemented with a
single fma).  And for 2^-25 <= |x| <= 2^-4, we use a single degree-8 minimax polynomial generated by Sollya.

Reviewed By: sivachandra, zimmermann6

Differential Revision: https://reviews.llvm.org/D121574